Vertebrates
February 25, 2008
Vocabulary
CephalochordataUrochordataVertebrataNotochordPharyngeal slitsAgnatha
GnathostomataChondrichthyesOsteichthyesAmphibiansmetamorphosisReptilia
Pterosaursamniotic eggArchaeopteryxAvesendothermicexothermicmammaliankeratin
OviparousviviparousMonotremesMarsupialsEutheriansmarsupiumarboreal
BrachiationPaleoanthropologyAustralopithecus africanus
1. Explain the characteristics of chordates.
Notochord – A longitudinal, flexible rod, located between the gut and the nerve cord
Dorsal, hollow nerve cord, invertebrates have solid ventral nerve cord
Presence of Pharyngeal slits
Muscular postanal tail
2. What are the characteristics present in the class vertebrata in addition to what are present in all chordates?
Cephalization very pronounced - Distinct brain encased in skeletal feature called a skull
Vertebral column that encloses the nerve cord
Closed circulatory system
3. Differentiate between Agnatha and Gnathostomata.
Agnatha- jawless vertebrates with cartilaginous skeleton, marine & freshwater, notochord persistent, lacking paired appendages
Gnathostomata- vertebrates w/hinged jaws, paired appendages, notochord replaced by vertebrae in adults of most spp.
4. What are the six classes of Gnathostomata?
A.Chondrichthyes --cartilaginous fishes
B.Osteichthyes -- bony fishes with ray fins or lobed fins
C.Amphibia -- frogs, toads, salamanders
D.Reptilia -- snakes, lizards, turtles
E.Aves – birds (now combined with reptiles)
F.Mammalia -- mammals
5. What are some of the characteristics of Osteichthyes (bony fishes)?
Presence of lateral lines that help sense the vibrations in water.
Respiration via gills
Swim bladder for buoyancy
Reproduction primarily w/external fertilization
6. Characteristics of Amphibians.
terrestrial, aquatic, or both
legless and gilled larval stage
smooth, permeable skin
egg w/o shell
w/external fertilization
Need water (or dampness) for eggs
7. What are the differences between larval and adult amphibians?
Larvae – lateral lines, gills, mostly live in water
Adults – no lateral lines, lungs, no tails as adults, can live both in water and land.
8. How are reptiles better adapted to terrestrial life than amphibians?
Scales or plates of keratin cover & protect body
Shell surrounding egg
Extra-embryonic membranes
Presence of amniotic eggs. Amnion - a fluid-filled sac
9. Archaeopteryxis the oldest known fossil with feathers, so considered the ancestor of birds.
10. What are some of the benefits of flight in birds?
exploitation of flying insects
better escape from land-bound predators
migration
10. What are some of the modifications in birds to enhance flight?
Reduced weight by eliminating some organs
a.Females have only one ovary
b.Birds lack teeth
Beak made of keratin
Excellent eyes
Wings covered with feathers
Hollow bones
11. Explain some of the characteristics of mammals.
Have hair (keratin)
Endothermic
4-chambered heart
Mammary glands
Most are viviparous – birth to living young
12. Ancestors of mammals weretherapsids.
13. What are three major groups of mammals?
A.Monotremes (egg layers) eg. platypuses and the echidnas (spiny anteaters)
Lay reptilian eggs, have hairs and mammary glands, found only in Australia and New Guinea.
B.Marsupials (pouch’s) eg. Opossums, kangaroos, koalas
Embryonic development is completed in a maternal pouch called a marsupium.
C.Placentals (Eutherians)
Complete embryonic development within the uterus–joined to mother by placenta
14. What are some of the features of primates?
1.Early primates were arboreal
2.Primates have limber shoulder joints for brachiation (swinging)
3.Dexterous hands
4.Claws were replaced by nails
5.Fingers became very sensitive
6.Eyes are close together in the front of the face
7.Hand-eye coordination
8.Parental care
9.Most primates have single births
10. Nurture their offspring for a long time
11. Opposable thumbs
15. Explain two hypotheses regarding the evolution of humans and which of those is the one supported by mitochondrial DNA and Y chromosomes analysis.
“out of africa hypothesis” Homo sapiens arose in Africa from H. erectus about 200,000 ya and moved to other places.
the “multiregional hyp” (H. erectus moved out of Africa)
Mitochondrial DNA, Y chromosomeanalysis supports the “Out of Africa hypothesis”.
16. Chimpanzeesare more closely related to humans than to other apes.